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|---|---|---|---|---|
| Cardinal | two hundred twenty-one | |||
| Ordinal | 221st (two hundred twenty-first) | |||
| Factorization | 13 × 17 | |||
| Greek numeral | ΣΚΑ´ | |||
| Roman numeral | CCXXI,ccxxi | |||
| Binary | 110111012 | |||
| Ternary | 220123 | |||
| Senary | 10056 | |||
| Octal | 3358 | |||
| Duodecimal | 16512 | |||
| Hexadecimal | DD16 | |||
221 (two hundred [and] twenty-one) is the natural number following220 and preceding222.
Its factorization as 13 × 17 makes 221 the product of two consecutiveprime numbers, the sixth smallest such product.[1]
221 is acentered square number,[2] anUlam number,[3] and a brilliant number,[4] meaning that its prime factors have the same amount of digits.
The year221 BC marked the end of theWarring States period and the beginning of theQin dynasty in China.[5]
221b Baker Street is the address of the fictional detectiveSherlock Holmes, created bySir Arthur Conan Doyle.[6]
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